Bipolar junction transistor heater circuit

ABSTRACT

An integrated circuit (IC) heater circuit comprises a drive circuit configured to increase the temperature of the IC when consuming power; a temperature sensor coupled to a control node of the drive circuit to activate and deactivate the drive circuit to provide an ambient temperature for the IC, wherein current of the temperature sensor varies with temperature; and a control circuit coupled to the temperature sensor and configured to adjust variation in the temperature sensitivity of the current of the temperature sensor.

CLAIM OF PRIORITY

This application is a Divisional Application of U.S. application Ser.No. 16/828,336, filed Mar. 24, 2020, which is incorporated by referenceherein in its entirety.

FIELD OF THE DISCLOSURE

This document relates to integrated circuits and in particular tocircuits that heat an integrated circuit die to provide a settemperature for operating the integrated circuit die.

BACKGROUND

Changes in temperature may change operating parameters of integratedcircuits. Temperature compensation in circuits is a concern forelectronic system designers. Many approaches have been used to achieveinsensitivity of circuits to ambient temperature changes.

SUMMARY OF THE DISCLOSURE

This document relates generally to integrated circuits and methods oftheir operation. In some aspects, an integrated circuit (IC) heatercircuit comprises a drive circuit configured to increase the temperatureof the IC when consuming power; a temperature sensor coupled to acontrol node of the drive circuit to activate and deactivate the drivecircuit to provide an ambient temperature for the IC, wherein current ofthe temperature sensor varies with temperature; and a control circuitcoupled to the temperature sensor and configured to adjust variation inthe temperature sensitivity of the current of the temperature sensor.

In some aspects, a method of operating an IC heater circuit comprisesconsuming power using a drive circuit of the IC; activating anddeactivating the drive circuit using a temperature sensor included inthe IC to control temperature of the IC, wherein current of thetemperature sensor varies with temperature; and adjusting variation intemperature sensitivity of the current of the temperature sensor using acontrol circuit included in the IC.

In some aspects, an IC comprises a voltage reference circuit; and an ICheater circuit. The IC heater circuit includes a drive circuit includinga resistive circuit load, wherein the drive circuit is configured toincrease the temperature of the IC by applying a drive current to theresistive circuit load; a temperature sensor coupled to a control nodeof the drive circuit to activate and deactivate the drive circuit toproduce an ambient temperature for the IC, wherein current of thetemperature sensor varies with temperature; and a control circuitcoupled to the temperature sensor and configured to adjust variation inthe temperature sensitivity of the current of the temperature sensor toreduce variation in the produced ambient temperature.

This section is intended to provide an overview of subject matter of thepresent Patent Application. It is not intended to provide an exclusiveor exhaustive explanation of the invention. The detailed description isincluded to provide further information about the present PatentApplication.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings, which are not necessarily drawn to scale, like numeralsmay describe similar components in different views. Like numerals havingdifferent letter suffixes may represent different instances of similarcomponents. The drawings illustrate generally, by way of example, butnot by way of limitation, various embodiments discussed in the presentdocument.

FIG. 1 is a block diagram of a heater circuit for an integrated circuit(IC) in an aspect.

FIG. 2 is a circuit diagram of a circuit for a temperature sensor in anaspect.

FIG. 3 is a plot of resistance of a pinch resistor and the value of abase voltage of a transistor of a temperature sensor in an aspect.

FIGS. 4A-4B contain a circuit diagram of a drive circuit for an ICheater circuit in an aspect.

FIGS. 5 and 6 are plots showing the variation in set temperature for twodifference temperature sensor circuits.

FIG. 7 is a flow diagram of an example of a method of operating an ICheater circuit.

DETAILED DESCRIPTION

As explained previously herein, temperature compensation in circuits canbe a concern. Many approaches have been used to achieve insensitivity ofcircuits to ambient temperature changes. In general, previous approacheshave attempted to design circuits with operating parameters that areinsensitive to changes in temperature. Another approach to addresstemperature compensation is to stabilize the temperature of the die byincluding a heater circuit in the die to maintain a steadyset-temperature in the die.

FIG. 1 is a block diagram of an example of an integrated circuit (IC)100 that includes a heater circuit 105. The heater circuit 105 sensesthe temperature of the IC and burns just enough power to increase theambient temperature of the IC to reach the pre-selected set temperature.

The heater circuit 105 includes a drive circuit 110, a temperaturesensor 115, and a control circuit 120. The drive circuit 110 increasesthe temperature of the IC when consuming power. In an example intendedto be non-limiting, the drive circuit 110 may apply a drive current to aresistive load to burn power to increase the temperature of the IC.

The temperature sensor 115 is coupled to a control node 125 of the drivecircuit 110. The temperature sensor 115 activates and deactivates thedrive circuit 110 using the control node 125 to provide an ambienttemperature for the IC. In some aspects, the temperature sensor 115pulls the voltage of the control node 125 towards circuit ground toreduce the drive current generated by the drive circuit 110. Reducingthe drive current reduces the power consumed by the drive circuit 110and reduces the heating produced by the heater circuit 105.

The magnitude of the current of the temperature sensor 115 varies withtemperature. This temperature sensitive current can be used to reducethe drive current of the drive circuit with increase in temperature. Insome aspects, the temperature sensitive current of the temperaturesensor 115 is a pull down current that pulls the control node towardcircuit ground to reduce the drive current of the drive circuit. Themagnitude of the current may increase with temperature to increase thedrive strength of a pull down circuit included in the temperature sensor115. Thus, the temperature sensor 115 reduces the drive current of thedrive circuit as temperature increases and provides negative circuitfeedback to the drive circuit 110.

Setting the temperature of the IC 100 allows operating parameters of theIC to be stable without using temperature insensitive circuits. Forexample, a voltage reference circuit 130 can be included in the IC.Because the set temperature of the IC is known, the voltage referencecircuit 130 can be designed to produce the desired voltage reference atthe set temperature, and the voltage reference circuit 130 does not needto be designed to provide the desired voltage reference over a range ofpossible temperatures.

A challenge of controlling the heater circuit 105 using a temperaturesensor 115 is achieving an accurate set temperature. Temperaturesensitivity of the temperature sensor 115 can vary with process. Theprocess variation may cause too much variation in the resulting settemperature of the heater circuit. This may cause too much variation incircuit operating parameters such as the reference voltage.

To resolve variation in temperature sensitivity, the control circuit 120adjusts variation in the temperature sensitivity of the current of thetemperature sensor with the result that the pre-chosen set temperatureof the heater circuit is achieved despite changes in variation oftemperature sensitivity due to variation in process.

FIG. 2 is a circuit diagram of an example of a circuit for a temperaturesensor 215. The temperature sensor 215 includes a bipolar junctiontransistor (BJT) 235 coupled to the control node 225 of the drivecircuit that provides a pull down current at the collector region thatvaries with temperature to the control node 225. The temperature sensor215 senses the temperature and causes the drive circuit to burn justenough power to heat the IC to reach the set temperature.

The temperature sensor circuit 215 includes a control circuit. Thecontrol circuit includes a bias circuit 240 configured to apply a biasvoltage to a base region of the BJT 235. The base emitter voltage(V_(BE)) is used to set the current at the collector to control thedrive circuit.

Upon circuit startup, the BJT 235 will be off at first because theforced V_(BE) voltage applied to it is not large enough at a lowertemperature to conduct and pull down the collector coupled to thecontrol node 225. This causes the drive circuit connected to the controlnode to be fully on at startup until the burned power increases thetemperature of the die and the BJT 235 is turned on. When the BJT 235turns on, the BJT collector pulls down on the control node until thepower being burned in the drive circuit is just enough for the circuitto stabilize and maintain a fixed set-temperature.

The current at the collector of the BJT 235 (I_(C)) can be expressed as

I _(C) =I _(SS)(e ^(V) ^(BE) ^(/V) ^(T) ).

where I_(SS) is the saturation current of the BJT 235. The settemperature of the IC heater circuit is determined by the I_(SS) of theBJT 235 and the forced V_(BE) applied to the BJT 235. The I_(SS) in turnvaries with temperature. If the V_(BE) is fixed, the current at thecollector of the BJT will vary with temperature. A challenge is that theI_(SS) of a BJT 235 varies over process and this means the settemperature of the IC heater circuit also varies with process. In someIC applications the uniformity of the set temperature can be veryimportant.

An approach to address unwanted variation in set temperature is to varythe V_(BE) bias to offset the variation in temperature sensitivity ofI_(SS). The variation in I_(SS) can be compensated by the forced V_(BE)not being a fixed voltage, but instead a voltage that also varies withprocess. The variation in V_(BE) should vary inversely with thevariation in I_(SS) of the BJT 235 so that the bias voltage provided bythe bias circuit varies temperature inversely with the variation ininversely with the pull down current provided by the BJT 235.

In the temperature sensor example of FIG. 2 , the bias circuit 240includes a resistive divider circuit that generates the bias voltage atthe base region of the BJT from a stable voltage (e.g., V_(DC) 245). Theresistive divider circuit includes a pinch resistor (Rpinch) having aresistance value that varies with temperature in a way that tracks thechange in I_(SS) of the BJT 235.

Because the resistance of the pinch resistor value tracks I_(SS), ifI_(SS) is less than nominal for the BJT 235, the resistance of the pinchresistor will also be less than nominal, and this will increase thevalue of the forced V_(BE) produced by the bias circuit. If I_(SS) ofthe BJT 235 is higher than nominal, the resistance of the pinch resistorwill move in the other direction to decrease the value of the forcedV_(BE). This compensation of V_(BE) helps to achieve a tighterset-temperature distribution for the IC heater circuit despite processvariations.

FIG. 3 is a plot of resistance of a pinch resistor and the value ofV_(BE). When the resistance value of the pinch resistor is high, thebias voltage V_(BE) is lower, and when the resistance value is low theV_(BE) is higher. Because the resistance value tracks I_(SS), the graphalso shows the correlation of I_(SS) and V_(BE). When I_(SS) is higher,the bias voltage V_(BE) is lower to compensate for the higher I_(SS) andreturn the temperature sensitivity of the BJT collector current tonominal. And when I_(SS) is lower, the V_(BE) is higher to compensatefor the lower I_(SS) to provide nominal temperature sensitivity for thecollector current.

FIGS. 4A-4B contain a circuit diagram of an example of a drive circuit410 of an IC heater circuit. The drive circuit 410 includes a resistivecircuit 430 as a circuit load. The drive circuit 410 applies a drivecurrent to the resistive circuit to burn power to increase thetemperature of the IC. The drive circuit 410 includes a control node425. Transistor 435 and pinch resistor (Rpinch) are included in atemperature sensor circuit that adjusts the voltage of the control node425 to adjust the drive current applied to the resistive circuit 430,and thereby adjusts the amount of power consumed by the drive circuit410 to adjust the temperature of an IC.

FIG. 5 is a plot showing the variation in set temperature for the ICheater circuit when a bias circuit without a pinch resistor is used tobias the BJT. The set temperature varies over a range from about 83° C.to 99° C. FIG. 6 is a plot showing variation in set temperature when abias circuit with a pinch resistor is used to bias the BJT. The settemperature is tightened to about 89° C.

The specific set temperature may be set by design of the BJT and thenominal value of V_(BE). The value of the set temperature of the heatercircuit decreases by roughly 9° C. when the size of the BJT is doubled.The value of the set temperature increases by 9° C. when the biascurrent of the BJT is doubled. Once the BJT is designed to select thedesired set temperature, the base voltage bias V_(BE) can be adjusted tocompensate for process variation in set temperature.

FIG. 7 is a flow diagram of a method 700 of operating an IC heatercircuit. At 705, power is consumed using a drive circuit of the IC toraise the temperature of the IC. This can be accomplished by applying acurrent to a resistive circuit load or by operating another type of ICcircuit to produce heat.

At 710, the drive circuit is controlled by a temperature sensor includedin the IC to activate and deactivate the drive circuit. In some aspects,a current of the temperature sensor varies with temperature, and thecurrent is used to reduce the drive current applied by the drivecircuit.

At 715, variation in temperature sensitivity of the current of thetemperature sensor is adjusted using a control circuit included in theIC. In some aspects, the temperature sensor includes a transistor toprovide the current to control the drive circuit. The control circuitprovides a bias voltage to the transistor that tracks temperatureinversely to the sensor current to compensate for variation intemperature sensitivity of the temperature sensor.

It can be seen that the devices and methods described herein overcomethe limitations of conventional approaches to temperature compensationof integrated circuits.

Additional Description and Aspects

A first Aspect (Aspect 1) can include subject matter (such as anintegrated circuit (IC) heater circuit) comprising a drive circuitconfigured to increase the temperature of the IC when consuming power; atemperature sensor coupled to a control node of the drive circuit toactivate and deactivate the drive circuit to provide an ambienttemperature for the IC, wherein current of the temperature sensor varieswith temperature; and a control circuit coupled to the temperaturesensor and configured to adjust variation in the temperature sensitivityof the current of the temperature sensor.

In Aspect 2, the subject matter of Aspect 1 optionally includes atemperature sensor configured to provide a pull down current thatincreases with temperature to the control node of the drive circuit; anda control circuit that includes a bias circuit configured to apply abias voltage to a base region of the BJT, and the bias circuit isconfigured to vary the bias voltage of the bias circuit with temperatureinversely to the pull down current of the BJT.

In Aspect 3, the subject matter of one or both of Aspects 1 and 2optionally includes a temperature sensor that includes a bipolarjunction transistor (BJT) coupled to the control node of the drivecircuit that provides a pull down current that varies with temperatureto the control node; and a control circuit includes a bias circuitconfigured to apply a bias voltage to a base region of the BJT, and thebias circuit is configured to vary the bias voltage of the bias circuitwith temperature inversely to the pull down current of the BJT.

In Aspect 4, the subject matter of Aspect 3 optionally includes a biascircuit includes a pinch resistor having a resistance that varies withtemperature.

In Aspect 5, the subject matter of Aspect 3 optionally includes aresistive divider circuit configured to generate the bias voltage at thebase region of the BJT, and the resistive divider circuit includes apinch resistor having a resistance that varies with temperature and thebias voltage generated by the resistive divider circuit varies inverselyto a temperature variation of a component of the pull down current ofthe BJT.

In Aspect 6, the subject matter of Aspect 5 optionally includes thecomponent of the pull down current of the BJT is a saturation current ofthe BJT and the BJT is sized to produce a saturation current thatcontrols the drive circuit to heat the IC to a specified temperaturethat is within the range of eighty to one hundred degrees Celsius (80°C.-100° C.).

In Aspect 7, the subject matter of one or any combination of Aspects 1-6optionally includes a resistive circuit. The drive circuit is configuredto apply a drive current to the resistive circuit to increase thetemperature of the IC, and the temperature sensor is configured toreduce the drive current of the drive circuit with increase intemperature.

Aspect 8 can include subject matter (such as a method of operating an ICheater circuit) or can optionally be combined one or any combination ofAspects 1-7 to include such subject matter, comprising consuming powerusing a drive circuit of the IC; activating and deactivating the drivecircuit using a temperature sensor included in the IC to controltemperature of the IC, wherein current of the temperature sensor varieswith temperature; and adjusting variation in temperature sensitivity ofthe current of the temperature sensor using a control circuit includedin the IC.

In Aspect 9, the subject matter of Aspect 8 optionally includesproviding a pull down current to a control node of the drive circuitusing the temperature sensor, wherein the pull down current of thetemperature sensor increases with temperature; and providing circuitfeedback to the temperature sensor that varies inversely with the pulldown current of the temperature sensor.

In Aspect 10, the subject matter of one or both of Aspects 8 and 9optionally includes providing a pull down current to a control node ofthe drive circuit using a bipolar junction transistor (BJT) included inthe temperature sensor circuit, wherein the pull down current of the BJTvaries with temperature; and forcing a bias voltage at a base region ofthe BJT to vary with temperature inversely with the pull down current ofthe BJT using the control circuit.

In Aspect 11, the subject matter of Aspect 10 optionally includessetting the bias voltage of the base region of the BJT using a biascircuit that includes a pinch resistor having a resistance that varieswith temperature proportional to the pull down current of the BJT.

In Aspect 12, the subject matter of Aspect 10 optionally includessetting the bias voltage of the base region of the BJT using a biascircuit that includes a resistive divider configured to generate thebias voltage using a circuit supply voltage; and varying the biasvoltage inversely to the temperature variation in pull down currentusing a pinch resistor included in the resistive divider circuit.

In Aspect 13, the subject matter of one or any combination of Aspects8-12 optionally includes turning on the drive circuit before turning onthe BJT upon a circuit startup, and the bias voltage generated by thebias circuit is less than a turn on voltage of the BJT at the circuitstartup.

In Aspect 14, the subject matter of one or any combination of Aspects8-13 optionally includes driving current through a resistive load of thedrive circuit to increase temperature of the IC; and activating anddeactivating the control node of the drive circuit using the temperaturesensor to increase and decrease the current through the resistive load.

Aspect 15 includes subject matter (such as an IC) or can optionally becombined with one or any combination of Aspects 1-14 to include suchsubject matter, comprising a voltage reference circuit and an IC heatercircuit. The IC heater circuit includes a drive circuit including aresistive circuit load, wherein the drive circuit is configured toincrease the temperature of the IC by applying a drive current to theresistive circuit load; a temperature sensor coupled to a control nodeof the drive circuit to activate and deactivate the drive circuit toproduce an ambient temperature for the IC, wherein current of thetemperature sensor varies with temperature; and a control circuitcoupled to the temperature sensor and configured to adjust variation inthe temperature sensitivity of the current of the temperature sensor toreduce variation in the produced ambient temperature.

In Aspect 16, the subject matter of Aspect 15 optionally includes atemperature sensor configured to provide a pull down current thatincreases with temperature to the control node of the drive circuit; anda control circuit configured to provide circuit feedback to thetemperature that varies inversely with the pull down current of thetemperature sensor.

In Aspect 17, the subject matter of one or both of Aspects 14 and 15optionally includes a temperature sensor including a bipolar junctiontransistor (BJT) coupled to the control node of the drive circuit thatprovides a pull down current to the control node that varies withtemperature; and a control circuit including a bias circuit configuredto apply a bias voltage to a base region of the BJT, and the biascircuit is configured to vary the bias voltage of the bias circuit withtemperature inversely to the pull down current of the BJT.

In Aspect 18, the subject matter of Aspect 17 optionally includes a biascircuit including a pinch resistor having a resistance that varies withtemperature inversely with the pull down current of the BJT.

In Aspect 19, the subject matter of Aspect 17 optionally includes a biascircuit includes a resistive divider circuit configured to generate thebias voltage at the base region of the BJT, wherein the resistivedivider circuit includes a pinch resistor having a resistance thatvaries with temperature inversely with a component of the pull downcurrent of the BJT.

In Aspect 20, the subject matter of one or any combination of Aspects17-19 optionally includes a drive circuit that turns on before the BJTtransistor upon a circuit startup, and the bias voltage generated by thebias circuit is less than a turn on voltage of the BJT at the circuitstartup.

These non-limiting Aspects can be combined in any permutation orcombination. The above detailed description includes references to theaccompanying drawings, which form a part of the detailed description.The drawings show, by way of illustration, specific embodiments in whichthe invention can be practiced. These embodiments are also referred toherein as “examples” or “aspects.” All publications, patents, and patentdocuments referred to in this document are incorporated by referenceherein in their entirety, as though individually incorporated byreference. In the event of inconsistent usages between this document andthose documents so incorporated by reference, the usage in theincorporated reference(s) should be considered supplementary to that ofthis document; for irreconcilable inconsistencies, the usage in thisdocument controls.

In this document, the terms “a” or “an” are used, as is common in patentdocuments, to include one or more than one, independent of any otherinstances or usages of “at least one” or “one or more.” In thisdocument, the term “or” is used to refer to a nonexclusive or, such that“A or B” includes “A but not B,” “B but not A,” and “A and B,” unlessotherwise indicated. In the appended claims, the terms “including” and“in which” are used as the plain-English equivalents of the respectiveterms “comprising” and “wherein.” Also, in the following claims, theterms “including” and “comprising” are open-ended, that is, a system,device, article, or process that includes elements in addition to thoselisted after such a term in a claim are still deemed to fall within thescope of that claim. Moreover, in the following claims, the terms“first,” “second,” and “third,” etc. are used merely as labels, and arenot intended to impose numerical requirements on their objects. Methodexamples described herein can be machine or computer-implemented atleast in part.

The above description is intended to be illustrative, and notrestrictive. For example, the above-described examples (or one or moreaspects thereof) may be used in combination with each other. Otherembodiments can be used, such as by one of ordinary skill in the artupon reviewing the above description. The Abstract is provided to complywith 37 C.F.R. § 1.72(b), to allow the reader to quickly ascertain thenature of the technical disclosure. It is submitted with theunderstanding that it will not be used to interpret or limit the scopeor meaning of the claims. Also, in the above Detailed Description,various features may be grouped together to streamline the disclosure.This should not be interpreted as intending that an unclaimed disclosedfeature is essential to any claim. Rather, inventive subject matter maylie in less than all features of a particular disclosed embodiment.Thus, the following claims are hereby incorporated into the DetailedDescription, with each claim standing on its own as a separateembodiment. The scope of the invention should be determined withreference to the appended claims, along with the full scope ofequivalents to which such claims are entitled.

What is claimed is:
 1. A method of operating an integrated circuit (IC)heater circuit, the method comprising: consuming power using a drivecircuit of the IC; activating and deactivating the drive circuit using atemperature sensor included in the IC to control temperature of the IC,wherein current of the temperature sensor varies with temperature; andadjusting variation in temperature sensitivity of the current of thetemperature sensor using a control circuit included in the IC.
 2. Themethod of claim 1, wherein deactivating the drive circuit includesproviding a pull down current to a control node of the drive circuitusing the temperature sensor, wherein the pull down current of thetemperature sensor increases with temperature; and wherein adjusting thevariation in the temperature sensitivity of the current of thetemperature sensor includes providing circuit feedback to thetemperature sensor that varies inversely with the pull down current ofthe temperature sensor.
 3. The method of claim 1, wherein deactivatingthe drive circuit includes providing a pull down current to a controlnode of the drive circuit using a bipolar junction transistor (BJT)included in the temperature sensor circuit, wherein the pull downcurrent of the BJT varies with temperature; and wherein adjusting thevariation in temperature sensitivity of the current of the temperaturesensor includes forcing a bias voltage at a base region of the BJT tovary with temperature inversely with the pull down current of the BJTusing the control circuit.
 4. The method of claim 3, wherein adjustingthe variation in temperature sensitivity of the current of thetemperature sensor includes setting the bias voltage of the base regionof the BJT using a bias circuit that includes a pinch resistor having aresistance that varies with temperature proportional to the pull downcurrent of the BJT.
 5. The method of claim 3, wherein adjusting thevariation in temperature sensitivity of the current of the temperaturesensor includes: setting the bias voltage of the base region of the BJTusing a bias circuit that includes a resistive divider configured togenerate the bias voltage using a circuit supply voltage; and varyingthe bias voltage inversely to the temperature variation in pull downcurrent using a pinch resistor included in the resistive dividercircuit.
 6. The method of claim 3, including turning on the drivecircuit before turning on the BJT upon a circuit startup, and the biasvoltage generated by the bias circuit is less than a turn on voltage ofthe BJT at the circuit startup.
 7. The method of claim 1, whereinconsuming power using a drive circuit of the IC includes driving currentthrough a resistive load of the drive circuit to increase temperature ofthe IC; and wherein the activating and deactivating the control node ofthe drive circuit using the temperature sensor increases and decreasesthe current through the resistive load.
 8. The method of claim 1,including providing a pull down current to a control node of the drivecircuit using a bipolar junction transistor (BJT), wherein a size of theBJT determines a set temperature of the IC and the activating anddeactivating the drive circuit sets ambient temperature of the IC to theset temperature.
 9. The method of claim 8, including producing areference voltage on the IC according to the set temperature.
 10. Themethod of claim 8, wherein the adjusting the temperature sensitivity ofthe current includes setting a collector current of the BJT using a baseemitter voltage (V_(BE)) of the BJT to control the drive circuit,wherein a process variation in the base emitter voltage varies inverselywith a process variation in saturation current of the BJT.
 11. Themethod of claim 8, wherein the adjusting the temperature sensitivity ofthe current includes setting a collector current of the BJT using aresistive circuit element of the IC to control the drive circuit,wherein a process variation in the resistive circuit element tracks theprocess variation in saturation current of the BJT.
 12. The method ofclaim 1, wherein consuming power using a drive circuit of the ICincludes driving a resistive circuit of the IC using current of thedrive circuit to heat the IC.
 13. The method of claim 1, including: thetemperature sensor providing a pull down current that increases withtemperature to the control node of the drive circuit; and the controlcircuit providing, to the temperature sensor, circuit feedback thatvaries inversely with the pull down current of the temperature sensor.14. An integrated circuit (IC) temperature setting circuit, the ICtemperature setting circuit comprising: a drive circuit to consume powerwhen activated; a temperature sensor configured to activate anddeactivate the drive circuit to set the IC to an operating settemperature, wherein current of the temperature sensor varies withtemperature; and a control circuit configured to adjust variation intemperature sensitivity of the current of the temperature sensor. 15.The IC temperature setting circuit of claim 14, wherein the temperaturesensor is configured to provide a pull down current to a control node ofthe drive circuit, wherein the pull down current increases withtemperature; and the control circuit is configured to provide circuitfeedback to the temperature sensor that varies inversely with the pulldown current of the temperature sensor.
 16. The IC temperature settingcircuit of claim 14, wherein the temperature sensor includes a bipolarjunction transistor (BJT) configured to provide a pull down current to acontrol node of the drive circuit to deactivate the drive circuit,wherein the pull down current of the BJT varies with temperature; andwherein the control circuit is configured to force a bias voltage at abase region of the BJT to vary with temperature inversely with the pulldown current of the BJT.
 17. The IC temperature setting circuit of claim16, wherein the control circuit includes a bias circuit to set a biasvoltage of the base region of the BJT, wherein the bias circuit includesa pinch resistor having a resistance that varies with temperatureproportional to the pull down current of the BJT.
 18. The IC temperaturesetting circuit of claim 16, wherein the control circuit includes a biascircuit to set a bias voltage of the base region of the BJT, wherein thebias circuit includes a resistive divider configured to generate thebias voltage using a circuit supply voltage, and vary the bias voltageinversely to the temperature variation in pull down current using apinch resistor included in the resistive divider circuit.
 19. The ICtemperature setting circuit of claim 16, wherein the drive circuit isconfigured to turn on before the BJT during a circuit startup, andwherein the control circuit includes a bias circuit to set a biasvoltage of the base region of the BJT, and the bias voltage is less thana turn on voltage of the BJT.
 20. The IC temperature setting circuit ofclaim 14, wherein the drive circuit provides current through a resistiveload of the drive circuit to increase temperature of the IC; and whereinthe temperature sensor is configured to increase and decrease thecurrent through the resistive load by the activating and deactivating ofthe control node of the drive circuit.